Wojcicki, Google's 16th employee, will lead YouTube, replacing co-founder of the online video service Salar Kamangar

SAN FRANCISCO -- YouTube has been a huge success in terms of traffic and even social impact since Google acquired it for $1.65 billion in 2006. But the online video service has not been a big source of revenue, and certainly not profit, for the world's largest Internet search provider.

This may be about to change as Susan Wojcicki, the long time head of Google's huge advertising business, becomes head of YouTube, replacing co-founder Salar Kamangar.

Wojcicki and Sridhar Ramaswamy have been jointly running the ads business at Google for a while and he will continue in that role when she moves to YouTube.

Wojcicki was Google's 16th employee and she famously rented her garage to co-founders Larry Page and Sergey Brin as they built their search engine in the late 1990s in Silicon Valley.

As Google grew, Wojcicki took on more responsibilities and now oversees all of the company's ad products, including AdWords, AdSense and DoubleClick. In this role, she has been responsible for well over half of Google's revenue, which totaled $55 billion last year.

"Given her high profile at the company, and experience with monetizing the core assets, this suggests Google is raising the bar at YouTube in terms of revenues and contribution," said Colin Sebastian, an analyst at RW Baird. "I would assume a bigger push with advertising, but also a higher profile role for YouTube at the executive table."

Wojcicki's move comes as YouTube woos more big brands which traditionally have spent heavily on TV advertising. The total brand advertising market, which includes digital, TV and more traditional offline ads, is worth at least $300 billion a year. As more of this spending shifts online, YouTube will be an important tool for Google to grab a big share of the money.

YouTube brought in $5.60 billion in gross ad revenue in 2013. After paying back ad partners and video content creators, the company netted $1.96 billion in ad revenue last year, up 66% from 2012, according to eMarketer estimates.

During a speech at an advertising technology conference in San Francisco last year, Wojcicki said Google is trying to give users more control over what ads they see online.

She highlighted TrueView, a type of YouTube ad that runs before a user's selected video begins. Advertisers only pay if the user chooses to watch the ad. If they skip it, no money changes hands.

"They are trying to bring in fresh perspective and figure out better ways to monetize YouTube," said Ben Schachter, an analyst at Macquarie. "While it's been remarkably successful, the user interface and general experience should have evolved more by now."